Despite the continuing publicity surrounding the prospects for true video-on-demand, the implementation costs involved in the delivery of programming on this basis remain prohibitive. In practice, a pay-per-view system might need to allocate a dozen or more "channels" for different viewers watching the same popular program, but offset in time by as little as one frame of video. When the utilization of the available transmission bandwidth is inefficient, the cost of delivery requires pricing levels that are unattractive to the viewer, particularly when compared with established delivery systems such as video rental stores or simply waiting for the movie to be scheduled on a premium cable channel.
As a consequence, current industry discussions are now centered around the concept of "near"-video-on-demand, in which the period of time a viewer is required to wait for a chosen program is minimized, typically by broadcasting the same program on several channels simultaneously, but offset in time by multiples of 10 or 15 minutes. In this manner, viewers need only wait until the next starting time, and then tune their cable converter box to the appropriate channel. This approach has a major disadvantage--the viewer must arrange to see the program during one of the periods in which it is available on cable TV. If the program is only scheduled at times when the viewer cannot be present, then the only alternative is to attempt to videotape the program for viewing at a later date, which, in the case of pay-per-view, will require special arrangements, as these program purchases are typically implemented by placing a telephone call at the time the purchase is to occur.
The prior art discloses several attempts which address at least some of the issues involved in facilitating pay-per-view purchases. For example, Baji et al., U.S. Pat. No. 5,027,400, describe the hardware requirements for implementing a video-on-demand system on a bi-directional broadcast system, in which a collection of server computers manage program and commercial databases. Data are assembled into cells to be transmitted to individual subscriber systems, using an Asynchronous Transfer Mode (ATM) packet transmission system for the broadband transmission line. Orders for program materials from subscribers are entered via the subscriber's network terminal and terminal control unit, employing the same broadband transmission line for the necessary communications to execute the transaction. However, few of the currently installed cable systems are capable of bi-directional transmission, which limits the applicability of this type of system in the short term.
At the present time, pay-per-view systems usually are implemented by employing connections to telephone lines to execute the transaction and initiate the program delivery process. Stetten et al., U.S. Pat. No. 3,746,780, discloses the use of a separate and independent telephone communications link to enable access to stored audio and video material, and Abraham, U.S. Pat. No. 4,590,516, discloses an improved system for such an application.
While these references establish the basic requirements for a pay-per-view type of system, they do not adequately address the formidable communications problems associated with the nearly-simultaneous access of a large number of subscribers to the transaction facilities. Bestler et al., U.S. Pat. No. 4,755,872, discloses the use of the Automatic Number Identification (ANI) services offered in many areas of the country, and exploit these capabilities to identify the subscriber and to forward the transaction information to the cable company's billing computer. A common feature of all of these systems is that the transaction (billing) occurs at the time the program is viewed, and this places a heavy burden on the communication facilities. In addition, completion of the ordering/billing transaction must precede the viewing of the program material.
Kauffman, U.S. Pat. No. 4,710,955, discloses a method and apparatus for implementing bi-directional communications between the billing computer and the subscriber apparatus. In this approach, the actual billing process is on a non-real-time basis, using a method referred to as "store-and-forward". Here, the subscriber purchases program credits (stored in the subscriber's terminal facilities) in advance, and these credits are debited when an order is placed for programming. The actual billing is recorded when a telephone communications link is established between the subscriber terminal and the cable company billing computer, at which time the subscriber's terminal reports the purchase to the billing computer. Although not explicitly disclosed, it is clear that a subscriber with good credit could be allowed to purchase a program even though he did not have an adequate supply of credits, and the supply could be replenished automatically when the subscriber's terminal unit contacts the billing computer.
A separate aspect of these systems is the method by which the security is implemented. It is the usual practice for a cable company to employ any of several well-known techniques for "scrambling" the premium channel program material, and rely on the subscriber's terminal facilities to de-scramble the signals for viewing. This de-scrambling process is authorized by the cable company's billing and transmission facilities, employing either the broadband transmission line or a separate telephone communication link. Arn et al., U.S. Pat. No. 4,535,355, Schilling et al., U.S. Pat. No. 4,621,285, Hamilton, U.S. Pat. No. 4,796,299, and Chomet et al., U.S. Pat. No. 4,916,737, disclose various methods for implementing the security by employing encryption keys and other such data security techniques.
Yurt et al., U.S. Pat. No. 5,132,992, disclose an audio/video transmission system which includes provisions for storage of program content at the cable system facility, at intermediate data-compressed storage libraries, or at the subscriber terminal site. The system disclosed relies on a complicated method of assembling program data into blocks for distribution onto a variety of transmission media at a range of transmission rates, but does not guarantee a uniform data rate. As a result, the subscriber receiving terminal requires buffering in the form of digital data storage means, so that the program may be played back at a later time, in real-time.
All of the systems discussed herein share the common feature that the purchase transaction occurs at the time of the program transmission, although the act of recording of the billing may be delayed for a period of time. If for any reason the viewing is interrupted or terminated, the viewer has no means by which he may cancel the transaction.